Roof Structure Research Articles

Research on Roof Weighting Mechanism of Coal Pillar Mining in Shallow Buried Closely Spaced Multi-seams

Abstract In the process of mining, the lower working face through the coal pillar (CP) in shallow-buried closely coal seams (SBCCS), noticeable roof step sinking, and dynamic load effects on the support were observed. In order to reveal the mechanism of strong ground pressure, the theoretical model of roof structure during the period of CP is established, and the calculation formula of the position of strong mine pressure is given. Taking the 22,408 working faces through the overlying concentrated CP of the Bulianta Coal Mine was selected as the research object. Using the methods of field measurement, physical simulation, and theoretical analysis to master the law of movement of the CP and overlying strata while passing the CP, the structural coupling impact of the key strata structure of the interburden and CP was revealed, which was the main reason for the cutting dynamic load effect during the passing of the CP of the working face. The advanced breaking mechanical model of the coupled roof structure of the “key strata structure of the interburden and the coal pillar” is established; the main factors affecting the breakthrough distance of the advanced breaking distance are analyzed; and the mechanism of the strong weighting caused by the cutting roof of the working surface is explained at the stage of CP. At the same time, it is obtained that when the width of the CP is 25 m, the working face is 20 m below the CP, which is the maximum bending moment point of the rock beam, indicating that the position that is prone to break under this width is about 5 m of the CP, which aligns with experimental data. The present study provides a theoretical guideline for the location and control of strong ground pressure during CP mining in SBCCS.

Green Roof Systems within the Framework of a Circular Economy: A Scoping Review

Green roofs are nature-based solutions with multiple benefits for the urban environment, but they have specific polymeric components in their structure that cause a carbon footprint. This scoping review highlights the technological advance in reusing or recycling alternative materials in green roof structures worldwide, making them a part of the circular economy (CE), and the search strategies to promote them to find whether there is a relation between them. The data were collected using the Web of Science from 2012 to 2022; we also used the Bibliometrix package to analyse research development by country and the development of the topic by author’s keywords. We selected 68 open-access articles from twenty-four countries and reviewed the grey literature from the top five productive countries on this topic. Our findings show that CE strategies are performed nationally, while the green roof promotion ones are concentrated at the city level. The theme co-occurrence analysis showed that the substrate is the primary layer used with alternative materials, and the three materials most applied for it are rubber, biochar, and hydrogel. It was found that the primary purpose of optimising green roofs with alternative materials is to increase the ecosystem services they provide and indirectly function within the circular economy; still, there is a gap in estimating the environmental impact of doing this as a potential CE activity.

Load history dependency of stiffness properties of PTFE-coated glass fibre membranes

The aim of this contribution is to investigate whether the order of load ratios applied to a textile structure impacts the biaxial stiffness behaviour of the structural textile itself. These investigations are performed based on biaxial tests on an architectural woven glass fibre fabric, a representative of such membranes. The first part of the paper investigates the existence and extent of load history dependency in the material response. Biaxial test results show that effects of a previous load history on the weave geometry cannot be eliminated by further load cycling in all biaxial stress ratios. Moderate to strong effects are recognized in two stress ratios, although not in both weave directions.The second part of the paper examines how these effects influence material stiffness parameters and structural calculations. Two boundary value problems are investigated: a pressure chamber test and a roof structure. Parameters obtained by fitting biaxial tests with or without history are considered. By incorporating an adaptive load-ratio dependent scheme, highly predictive numerical results are obtained, showing that while the effect of load history may appear small in the biaxial tests and pressure chamber test, it can be significant in complex structural problems like roof structures.

Shaking table test on progressive collapse of the double-layer cylindrical reticulated shell with infilled wall

Double-layer cylindrical reticulated shell has made rapid development in recent decades in China, which is widely used in the large-scale public buildings such as gymnasiums, airplane terminal, Shopping mall, etc. Stability and progressive collapse mechanism have been attracting a lot of attention because the large span space structure is largely affected by the geometry nonlinear, which makes it sensitive to the local damages. The infilled wall has a greater impact on the stiffness of the lower supporting structure due to sparse column grid. However, the influence of infilled walls on the collapse mechanism of large-span spatial structures is very complex due to the coupling of upper and lower structures. Therefore, the effects of infilled walls on double-layer cylindrical reticulated shell was investigated by a series of progressive collapse tests with shaking table. In order to evaluate the seismic performance and the capacity of resisting progressive collapse, the structural dynamic characteristics and response laws were obtained under different ground motions and input principal directions. The results indicated that the existence of infilled wall made the coupling between the lower supporting structure and the upper roof structure more complicated. The infilled walls influenced the structural damage evolution and development, mitigated the damage from the earthquake and changed the progressive collapse pattern, which made the catenary collapse mechanism occur when the structure collapsed. Although the further quantitative study is still needed, this paper provides lots of useful test data and conclusions, which gives references to the infilled wall design and seismic performance evaluation for double-layer cylindrical reticulated shell.

The prediction on non-Gaussian characteristics of wind pressure for the long-span roof in the mountainous area using proper orthogonal decomposition–deep learning framework

To make an accurate prediction of the non-Gaussian characteristics of wind pressure for the long-span roof, this study combines the proper orthogonal decomposition (POD) technique, convolutional neural network (CNN), and long short-term memory (LSTM) network to propose a novel POD-CNN-LSTM framework. Then, the proposed framework was well validated based on the wind tunnel testing of a long-span roof structure, and some error criteria, such as mean square root error and correlation coefficient, were adopted to evaluate the prediction accuracy of the non-Gaussian characteristics. Furthermore, two other methods, POD-CNN and POD-LSTM, were also used to conduct a comparative study. The obtained results illustrate that compared to POD-CNN and POD-LSTM, the proposed framework can achieve better performance on the pulsating wind pressure coefficient. For predictions of non-Gaussian characteristics, the output results of the proposed POD-CNN-LSTM show fewer errors, which means the predictions are close to the measured results, including skewness, kurtosis, and wind pressure probability density distributions. To summarize, the proposed POD-CNN-LSTM framework shows superiority over others, which means the proposed framework has good potential for the practical application of non-Gaussian prediction of the engineering structure.

The Jajarkot Earthquake: Revealed the Vulnerability of Load Bearing Structures in Western Nepal

The Jajarkot Earthquake, which occurred on 3rd November, 2023 of magnitude 5.7 (Mw) exposed Nepal’s longstanding vulnerability to seismic activity. This paper presents damage assessments derived from both on-site field observations and secondary resources to evaluate the damages sustained by load bearing masonry structures. In the region, 95% of the building structures are based on masonry construction. The damage status of structures in Jajarkot and Rukum East highlighted that about 50% of the building structures were partially and complete damage. The evaluation encompassed various aspects, including the types, mechanisms, and underlying causes of the damage incurred by structures. The observed damage was categorized using an established catalogue originally developed for the identification of failure mechanisms and vulnerability assessment. The common types of damage encompassed features like cracks in the load bearing external walls and corners, diagonal cracks originating from door and window corners, vertical out-of-plane displacement of external walls, collapse of external walls, and partial collapse of load bearing internal walls, fracturing of window and door lintels and complete collapse of structure. Some special forms of damage which was of new nature and distinct from those observed in prior seismic events such as the Gorkha earthquake included ruptures in the outer surfaces of loadbearing external walls, partial roof structure collapses, out-of-plane fragmentation or disintegration as well as rupture. The causes underlying this general damage were attributed to irregular bonding systems, weak mortar, stone block formation, size of stone blocks, absence of tie beams, weakly connected corners, insufficient connections of wall-roof and wall-floor systems, and differing internal wall systems. The mechanisms of damage varied based on the number and specifics of these causative factors, as well as certain structural attributes.

Classification of equivalent static wind loads: Comparisons and applications

This paper reviews the basic ideas, developments, and codification practices of different calculation methods for equivalent static wind load (ESWL) in the past about sixty years. From the landmark work of Davenport's Gust Loading Factor (GLF), Kasperski's Load-Response-Correlation (LRC), and Katsumura, Tamura's Universal-ESWL (U-ESWL), the development thread of ESWL is clarified. The ESWLs are classified based on the number of target load effects (Single-target or Multiple-target) and on actuality (Realistic or Unrealistic). GLF is representative as a “Single-target Unrealistic” ESWL, which has been adopted in many international codes and standards for building design and is extended into many approaches considering different targets (e.g. base bending moment), and different components (along-wind, crosswind, torsional). The LRC method identifies a realistic wind load distribution that causes one target maximum/minimum load effect, is a representative of “Single-target Realistic” ESWL, is well adopted as a background component ESWL, and is further developed to consider the dynamic resonant effect. The U-ESWL simultaneously reproduces maximum/minimum load effects in multiple structural members with only two sets of load distributions, is a “Multiple-target Unrealistic” ESWL, and has also been developed and employed in a wind load code for roof structures.

Fabrication of superamphiphobic micro-reentrant structures by inverted electrochemical deposition

Due to excellent oil resistance and shortened liquid-solid contact time, superamphiphobic surfaces have promising application prospects in oil transportation, and petroleum pollution control. Although superamphiphobic surfaces have been constructed on various substrates, there is still a lack of high-efficient methods for fabricating micro-reentrant structures on engineering metal substrates. This paper proposes a new method combining laser processing and inverted electrochemical deposition techniques to achieve high-efficient and large-scale fabrication of superamphiphobic surfaces on copper substrates. Firstly, micropillar array structures are constructed by laser processing, and the structures exhibit excellent superhydrophobicity after low surface energy modification. Then, inverted electrochemical deposition is performed after polishing the top of the array, and local angle of the gas/liquid interface can be controlled by adjusting the distance between the top of the micropillar and the electrolyte level, thus regulating micro-morphology of the roof structure. The influences of electrochemical deposition parameters on characteristics of the micro-reentrant structures are systematically investigated. Finally, superamphiphobic micro-reentrant structures (roof diameter > 190 μm, micropillar spacing <250 μm) with water and oil contact angles exceeding 150° are prepared after lowering the surface energy of the deposited structures. After anti-fouling, blowing, ultrasonic vibration, and tape adhesion tests, the prepared superamphiphobic micro-reentrant structures maintained good water and oil repellency, showing excellent chemical stability and durability. The research may provide a simple, efficient, and low-cost method for high-efficient constructing superamphiphobic surfaces on engineering metal substrates, enriching the fabrication techniques of micro-reentrant structures and facilitating their practical applications.

Quantitative Research on Roof Deformation and Temporary Support Stiffness in Deep-Mine Gob-Side Entry Retaining by Roof Cutting

The important technical process to ensure the success of gob-side entry retaining by roof cutting (GERRC) was the advanced pre-splitting blasting to cut off the mechanical connection between the roadway and working face roof. The whole-cycle roof structure evolution and stress characteristics of GERRC were analyzed. The factors affecting the roof deformation of GERRC were analyzed, and the quantitative relationship between the roof deformation of GERRC and the support stiffness was determined. The results showed that the temporary support stiffness was higher, the support position to the side of the roof cutting was closer, and the roof subsidence deformation of GERRC was smaller. It is proposed to use a single support mass with a high stiffness to control the deformation of the roof, but it also made the support mass and roof elastic potential energy aggregate. To fully utilize the matching of the support stiffness and roof subsidence, improve the stability, and control the subsidence deformation of the roof in GERRC, double-row stacking supports were adopted in the inclination of GERRC, which were used to increase the stiffness of the support system.

Availability and Consumption of Wooden Resource for the Construction of Late Medieval Roof Structures in Finland

Availability and Consumption of Wooden Resource for the Construction of Late Medieval Roof Structures in Finland

Development of Wood-Plastic Soil Tray Composite (WPSTC) Using Polymerized Coir-Wood Dust for Green Roof Structures

Development of Wood-Plastic Soil Tray Composite (WPSTC) Using Polymerized Coir-Wood Dust for Green Roof Structures

Three-Dimensional Physical Test Study on the Overburden Breaking Behavior of Non-Penetrating Pre-Splitting in Small-Coal-Pillar Roadway Roofs

In longwall coal mining, significant deformation of small-pillar roadways presents challenges for the safe and efficient retreat of mining panels. Non-penetrating directional pre-splitting alters the roof structure of these roadways and effectively manages their stability under high stress during mining operations. In this study, a three-dimensional experimental model for the non-penetrating pre-splitting of small-coal-pillar roadway roofs was established, the apparent resistivity change in the rock layer during mining of the working face was determined, the propagation law of high-frequency electromagnetic waves in the overlying rock was studied, and the stress distribution law of the surrounding rock was investigated. After non-penetrating pre-splitting in the roof, the apparent resistivity change rate of the overlying rock increased and the electromagnetic waveform exhibited scattering and diffraction, forming a short cantilever beam. After mining, the stress in the adjacent mining panel gateway reduced, resulting in a pressure relief effect on the surrounding rock. These findings were further validated through field application, where the overall deformation of the roadway was reduced by 57%. The research results shed light on the management of roof control in small-coal-pillar roadways and the rational determination of non-penetrating pre-splitting parameters.

Complex Heat Exchange of Structures Taking Into Account Radiation Cooling in Indoor Ice Rinks

Statement of the problem. The aim of the work is to construct a numerical model of complex radiation-convective heat exchange of the roof structures of an indoor skating rink with moist air of the upper zone to identify the dependencies of the increase in the velocity and area of condensation of water vapor on the height of the room Results. Based on the results of a numerical study of the process of complex non—stationary heat exchange of the system «surface of the floor structure — indoor air –– ice surface», theoretical dependences of the increase in the velocity and area of condensation of water vapor from the vertical coordinate under the action of radiation cooling from the ice field were obtained for the first time. Conclusions. The obtained dependences allow us to theoretically justify the choice of rational technical solutions and operating modes of ventilation and air conditioning systems in the upper zone to prevent condensation on the internal surfaces of building and enclosing structures.

Macro- and micro-anatomical investigation of the oropharyngeal roof of landform greek tortoise (Testudo graeca graeca) and semi-aquatic red-eared slider turtle (Trachemys scripta elegans)

The present investigation examined the oropharyngeal roof of two turtles having different feeding behaviors: the landform Greek tortoise (Testudo graeca graeca) primarily herbivores and the semi-aquatic red-eared slider turtle (Trachemys scripta elegans) lives in freshwater that opportunistic omnivorous grossly and by scanning and light microscopes. Grossly, the Greek tortoise had a V-shaped roof consisting of the upper rhamphotheca, peri-palatine region, upper alveolar ridge, peripheral palatine ridge, median palatine ridge, vomer, choanae, caudal palatine part, and pharynx. At the same time, the red-eared slider had a semilunar roof consisting of upper rhamphotheca, two peripheral palatine ridges, core of palatine ridges, upper alveolar band, vomer, choanae, caudal palatine part, and pharynx. SEM revealed that the red-eared slider roof appeared more straightforward. The upper rhamphotheca is sharp, with a median premaxillary notch in the red-eared slider that gives a powerful bite for cutting to compensate absence of the teeth. Additionally, the red-eared slider’s upper alveolar band is interrupted by a single upper alveolar ridge that appears spiky, pointed, and longer as it needs powerful chewing of prey and there are two types of teeth-like projections at its peri-palatine area for food-crushing and chewing. The Greek tortoise palatine region had numerous ridges and folds to provide roughness for food processing. Greek tortoises had small-sized choanae with two choanal folds to minimize choanal openings when eating dusty grasses. Histologically, Greek tortoise palate was rostrally thicker and more keratinized than caudally, and the caudal palatine region was characterized by a single pair of circumvallate-like papilla with multiple mucous openings and secretions, while red-eared slider palate was slightly keratinized at the peri-choanal region, and the rest of the palate was non-keratinized with few mucous openings. The current investigation found various structural oropharyngeal roof adaptations to feeding behavior in the omnivore red-eared slide compared to the herbivorous Greek turtle.

Compound 3D building modeling with structure-aware partition and primitive assembly from airborne laser scanning point clouds

ABSTRACT Urban digital twins and realistic three-dimensional (3D) scenes have further enhanced the ever-increasing demand for building models. Airborne Laser Scanning (ALS) point clouds are the predominant data source for 3D building reconstruction owing to their highly detailed spatial features. However, information on the reconstruction of compound buildings (i.e. buildings with diverse plane structures or various roof structures) is lacking. Existing methods often produce building models that suffer from topological inconsistencies and/or geometric errors. To address these issues, this study proposes an automatic building reconstruction approach based on ALS point cloud that offers both modeling flexibility and geometric consistency. Specifically, a structure-aware partitioning algorithm that partitions a complex building roof into several regular roof patches is incorporated. Subsequently, a primitive model library comprising representative primitives suitable for building reconstruction is created. Suitable primitive model selection and reconstruction optimization are employed to ensure the accuracy and compactness in the final model. To comprehensively evaluate the performance, two typical ALS point cloud datasets are tested. Experiments demonstrate the generated models can achieve a boundary consistency of 92% while ensuring Root Mean Square Error below 0.09 m. Comparative experiments with state-of-the-art methods further validate the effectiveness of the proposed approach in compound building reconstruction.

Enhancing the aerodynamic performance of large-span roof using a ‘breathable’ optimization tube: A parametric study

In wind engineering community, large-span roofs are widely acknowledged to be wind-sensitive, and oftentimes aerodynamic optimization is needed to enhance its wind-resistance. For such purpose, we proposed a “breathable” aerodynamic optimization tube in this study, the performance of which was experimentally examined via a series of wind tunnel tests. The results showed that, the proposed aerodynamic optimization tube is capable to significantly reducing the wind loads on the large-span roof, the effectiveness of which varies with different tube parameters. On this account, the effect of six key parameters, namely section shape, inlet-outlet angle, hole size, in-out ratio, hole distance and inlet hole length were examined independently. Overall, the outcomes are expected to provide important implications regarding the wind-resistance design of large-span roof structures.

Wind-induced interference effect of complex building clusters on long-span roof structures

The presence of complex buildings introduces interference effects and complicates the wind field around the long-span roof structure. The complexity of the problem makes it challenging to predict wind load of long-span roof structures, resulting in a scarcity of design data available to engineers and designers. Thus, the influence of interference effect on mean and peak pressure coefficients of a long-span tri-centered cylindrical roof structure was investigated through wind tunnel tests conducted in an atmospheric boundary layer wind tunnel. The study focused on the interference effects caused by two cooling towers, chimney, and some low-rise buildings, considering all wind directions. The results show that the interference effects are the result of a combination of amplification effects from the adjacent cooling towers and chimney and shielding effects from the surrounding low-rise buildings. Due to the shielding effect of low-rise buildings, the wind suction on the roof is mitigated compared to that of a single building, while at the end of the roof, wind suction is amplified by cooling tower effects. The interference effect of the building clusters, however, amplifies the fluctuating wind pressure coefficient and the peak pressure coefficient on the roof. To accurately estimate the wind load of building components and envelopes, furthermore, this study investigates the influence mechanism of interference effect on non-Gaussian characteristics of wind pressure combining with fluctuating wind pressure spectrum, spatial correlation of fluctuating wind pressure, and probability distribution characteristics of standardized wind pressure coefficient. The spatial correlation of wind pressure in the roof interference area exhibits a strong association, and the probability density distribution characteristics of the standardized wind pressure coefficient significantly deviate from the Gaussian curve, with a peak factor exceeding 3.5. Thus, it can be concluded that the wind pressure within this region demonstrates significant non-Gaussian characteristics. Hence, the zone values of peak pressure coefficients are determined using the peak factor approach to inform the wind resistance design of the envelope structure.

Pengaruh Angin Terhadap Tata Letak dan Jumlah Sekrup Konstruksi Baja Ringan Berdasarkan SNI-7971- 2013

Light weight steel material has experienced rapid development in the construction. However, there are still many costruction failures on light weight steel, resulting in cost loss. The failure of light steel structures often occurs at the connections. The connection tool on milld steel is usually using a self-drilling screw. The research location is at Aceh One Stop Integrated Service and Investment Service Building (DPMPTSP) Aceh. The problem in this study is the placement and number of screws on the lightweight steel roof structure in the field which is carried out for each member according to the code, and the effect of wind load on the placement and number of screws on the lightweight steel roof structure. This study aims to determine the effect of the placement and number of screws on the lightweight steel roof structure. The scope of this research of problems including the placement and number of screws on the lightweight steel roof structure. The standars used in the design of light steel structures in this study is SNI 7971 2013 and the loading planning standars using SNI 03 1727 1989. Calculation steps using the LRFD method for steel structure design regulated in SNI 03 1729 2002. Based on the results, it is obtained that the number and placement of the screws in the field are different from those obtained in the calculation. From the calculations, it is obtained from the recapitulation, dead loads with a maximum value of 123.07 kg, live loads with a maximum load of 30.1 6 kg, and for compressed air and suction loads with a maximum load of 180 kg. the maximum design force value is 1241.33 kg and the screws bearing resistance value is 256.752 kg. the number of screws is obtained where the the value of the design force is divided by the value of the bearing resistance, on each member obtained 1screw, 2 screws, 3 screws, 4 screws, and 5 screws. Whilst it is found for each member in the field using 3 screws.

Bearing mechanism of roof and rib support structure in automatically formed roadway and its support design method

Bearing mechanism of roof and rib support structure in automatically formed roadway and its support design method

Mechanical properties of hoberman radially retractable roof structures

In this paper, a spatial Hoberman radially retractable grid shell is constructed based on its planar version and the mechanical properties of the grid shell are analyzed using ABAQUS commercial software. The analysis shows that given carefully chosen parameters, the spatial grid shell can meet the requirements of the specification. Based on this, the influence of the number of multi-angulated rods, the number of segments of the multi-angulated rod, and the rise-span ratio on the mechanical performance of the structure are analyzed. The results show that the increase of the number of multi-angulated rods is beneficial to the mechanical properties of the structure, but will have a negative effect on the economic performance. To reach an optimized configuration, it is chosen such that the number of multi-angulated rods is 18, the steel consumption and the structural performance response are smaller. The decrease of the number of segments of the multi-angulated is beneficial to the mechanical properties, service performance, and economic performance of the structure, but considering the feasibility of processing, transportation and the driving condition setting, it is recommended to choose 4 segments of the multi-angulated rod. Higher rise-span ratio is beneficial to the mechanical properties of the structure in the closed state, but will adversely affect the mechanical properties and economic performance during the deployment.